桩筏基础相互作用非线性简化分析

Analysis of interaction mechanism of piled raft foundation by use of simplified nonlinear model

提出一种桩筏基础相互作用的简化分析方法。对筏板和土体的接触面进行单元离散,在单桩弹塑性分析的基础上,分析了桩–桩、桩–土、土–土的相互作用关系。推导了桩土体系的刚度矩阵,得到刚性筏板群桩基础的竖向荷载沉降关系,桩的轴力沿深度的分布和桩、筏板各自分担的荷载。无需对桩和土体沿深度方向进行单元离散,简化了计算过程。由于考虑了土体的非均匀性和桩土相互作用的非线性特性,计算模型更好地反映了土体的实际性状。与有限元、边界元计算值以及实际工程实测值进行对比分析,验证了本文方法的正确性,并可应用于实际工程问题的分析。

A simple and practical approach was presented for the analysis of behavior of vertically loaded pile groups embedded in homogeneous and nonhomogeneous soil with the rigid raft in contact with the ground. The interface between soil and raft was divided into a number of approximate square discrete elements. Based on the elasto-plastic analysis of single pile, the interactions between pile and pile, pile and soil, soil and soil were taken into account to determine the stiffness matrix of pile group-soil system. Then the vertical load-settlement relationship of piled raft foundation, axial load distribution in the piles along the depth and the load shared by piles and rafts were obtained. There was no need of discretization of soil and piles along pile shaft in the analysis. Therefore, the solving procedure was simplified. For considering the strength of soil varying along the depth and nonlinear interaction between piles and soil, the theoretical model agreed with the fact quite well. Comparison among the results of the finite element, boundary element, the field tests and the calculated results was carried out, and the feasibility of the present method for the analysis of piled raft foundation was proved.